1. Field of the Invention
The present invention relates to a method, device, and producing program of an elemental image array for three-dimensional image display.
2. Related Art
Parallax information that can be recognized by a viewer moving in a horizontal direction and viewing a two-dimensional image facing the viewer involves only horizontal movement of the two-dimensional image. If the two-dimensional image is located in front of the point of gaze, the two-dimensional image moves in the opposite direction from the viewer. If the two-dimensional image is located behind the point of gaze, the two-dimensional image moves in the same direction as the viewer. Accordingly, in a case where a two-dimensional image is to be displayed on a three-dimensional image display device of a horizontal parallax type, images obtained by shifting the two-dimensional image (hereinafter referred to as the original image) can be used as viewpoint images (as disclosed in JP-A 11-98529 (KOKAI), for example). By adjusting the amount of horizontal shifts, the near-side or far-side display position on a three-dimensional display can be changed.
Also, there has been suggested a method of displaying a two-dimensional image having a higher resolution than that of a three-dimensional image display device by employing the design in which two or more pixels are viewed through exit pupils (hereinafter, referred to as crosstalk). In this method, the information represented by the pixels to be viewed through the lenses is parallax information, and is also image information to be interpolated between adjacent lenses (hereinafter, referred to as interpolating effect). To achieve the interpolating effect, the display position of the two-dimensional image to be displayed needs to be slightly shifted from the surface of the three-dimensional image display device. More specifically, in a case where a lens array formed with cylindrical lenses (exit pupils) is employed as a light-ray control element, and where the distance between the lens array and the pixels for two-dimensional image display is shorter than the focal distance of the cylindrical lenses, two or more sets of parallax information are viewed in the forward order through the cylindrical lenses (a virtual image). In other words, the two or more sets of parallax information viewed through the cylindrical lenses are interpolated between the sets of information of the cylindrical lenses, by displaying the two-dimensional image in a far-side position in which the parallax information of the elemental image array is arranged in the same direction as the two-dimensional image (see JP-A 2005-091623 (KOKAI)).
In a case where an elemental image array is to be produced through horizontal movement of two-dimensional image information, and where the resolution of the original image is equal to or close to the resolution of the three-dimensional image display device, the display position is changed discretely. If the resolution of the original image is sufficiently high compared with the resolution of the three-dimensional image display device, such a problem is not caused. However, with the rendering efficiency being taken into consideration, the resolution of the original image often needs to be at least the same as the resolution of the three-dimensional image display device. If the horizontal movement of the two-dimensional image information is carried out only by the pixel unit, the range of the depth position the depth position in which the two-dimensional image can be displayed is greatly restricted. So-called “sprite processing” is known for reducing the load of image rendering. Since a number of viewing points are required for each frame in a three-dimensional displaying operation, sprite display is highly beneficial. However, if the depth position is only discretely set, an animation in which the depth position is continuously changed cannot be achieved.
In addition to that problem, in the above case where an elemental image array is to be produced through horizontal shifts of a two-dimensional image, parallax information is not obtained at all in the vertical direction. Because of that, the width of the two-dimensional image becomes larger in a nearer position, and becomes smaller in a farther position. However, the height is invariable with regular horizontal movements. As a result, the aspect ratio of the two-dimensional image is unbalanced, and the resultant image becomes unnatural, with the two-dimensional images displayed on the near side being enlarged in the horizontal direction and the two-dimensional images displayed on the far side being enlarged in the vertical direction.
Lastly, to produce an elemental image array having an interpolating effect, the depth position for achieving the most effective interpolating effect is unclear. Even if an elemental image array with varied far-side positions is produced by viewing elemental image arrays having different far-side display positions with eyes so as to determine the optimum far-side and near-side display positions, the obtained values are discrete, and it cannot be made clear whether the determined positions are the optimum positions.